1. Field of the Invention
The present invention relates to a method and apparatus for inspecting a solid-state image pickup device that detect a defect from an image signal coming from the solid-state image pickup device.
2. Description of the Invention
A solid-state image pickup device, for example an interline transfer type CCD (Charge Coupled Device) 11 has a plurality of photoreceptors 2 (photoelectric converter) for performing photoelectric conversion such as PN-junction photodiodes arranged two-dimensionally in horizontal and vertical directions. Vertical charge transfer paths 4 are respectively arranged for the plurality of photoreceptors 2 arranged in column direction (vertical direction). Between each photoreceptor and vertical charge transfer path 4 is placed a transfer gate 3. At one end of each vertical charge transfer path is arranged a horizontal charge transfer path 5. At the tip of the horizontal charge transfer path 5 in the data transfer direction is provided an output amplifier 6.
The photoreceptor 2 performs photoelectric conversion of irradiated light and accumulates signal charges having a charge amount corresponding to the light amount. When the transfer gate 3 is opened, the accumulated signal charges are simultaneously read onto the vertical charge transfer path 4 from each photoreceptor 2. The vertical charge transfer path 4 shifts the read signal charges and vertically transfers them by way of a vertical transfer clock to transport them to the horizontal charge transfer path 5. The horizontal charge transfer path 5 shifts the signal charges transported from the vertical charge transfer path 4 in the output amplifier 6 byway of the horizontal transfer clock. The output amplifier amplifies the signal charges and outputs them as a voltage signal.
When intense light is irradiated onto some of the charge transfer paths 2 and the resulting signal charges fills up the capacity of the photoreceptor 2, excessive charges flow into peripheral photoreceptors 2, which causes signal charges to be output from the photoreceptors 2 that do not receive light. As a result, the periphery the light does not reach appears also bright, a so-called blooming phenomenon. As shown in FIG. 5, blooming causes high-level vertical lines 8A or low-level vertical stripes 8B to appear in an image 7 thus dramatically degrading the picture quality.
As related art inspection method and inspection apparatus capable of detecting such spot blooming, a method and apparatus are known for performing vertical median processing, vertical addition and differential processing on image data and comparing the resulting value with a standard value to judge whether the data is good (for example, see JP-A-2004-40508).
The inspection method and inspection apparatus described in JP-A-2004-40508 perform evaluation of an image while focusing on a single blooming area at a particularly high level. When a high-level vertical line is there, it is difficult to determine the other vertical stripe defects. Even when numerous spot blooming areas are found, only some of them can be detected. Thus, in case a large number of spot blooming areas are there each of which is at an acceptable low level, the entire image is sometimes judged good although the picture quality could be adversely influenced. This prevents high-accuracy evaluation of an entire image.